Publications


Theory of Thomson scattering in inhomogeneous media.

Scientific reports 6 (2016) 24283-

PM Kozlowski, BJ Crowley, DO Gericke, SP Regan, G Gregori

Thomson scattering of laser light is one of the most fundamental diagnostics of plasma density, temperature and magnetic fields. It relies on the assumption that the properties in the probed volume are homogeneous and constant during the probing time. On the other hand, laboratory plasmas are seldom uniform and homogeneous on the temporal and spatial dimensions over which data is collected. This is particularly true for laser-produced high-energy-density matter, which often exhibits steep gradients in temperature, density and pressure, on a scale determined by the laser focus. Here, we discuss the modification of the cross section for Thomson scattering in fully-ionized media exhibiting steep spatial inhomogeneities and/or fast temporal fluctuations. We show that the predicted Thomson scattering spectra are greatly altered compared to the uniform case, and may lead to violations of detailed balance. Therefore, careful interpretation of the spectra is necessary for spatially or temporally inhomogeneous systems.


Residual zonal flows in tokamaks and stellarators at arbitrary wavelengths

PLASMA PHYSICS AND CONTROLLED FUSION 58 (2016) ARTN 045018

P Monreal, I Calvo, E Sanchez, FI Parra, A Bustos, A Koenies, R Kleiber, T Goerler


Characteristics of betatron radiation from direct-laser-accelerated electrons

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics (2016)

PA Norreys


Transport coefficients of a relativistic plasma.

Physical review. E 93 (2016) 053208-

OJ Pike, SJ Rose

In this work, a self-consistent transport theory for a relativistic plasma is developed. Using the notation of Braginskii [S. I. Braginskii, in Reviews of Plasma Physics, edited by M. A. Leontovich (Consultants Bureau, New York, 1965), Vol. 1, p. 174], we provide semianalytical forms of the electrical resistivity, thermoelectric, and thermal conductivity tensors for a Lorentzian plasma in a magnetic field. This treatment is then generalized to plasmas with arbitrary atomic number by numerically solving the linearized Boltzmann equation. The corresponding transport coefficients are fitted by rational functions in order to make them suitable for use in radiation-hydrodynamic simulations and transport calculations. Within the confines of linear transport theory and on the assumption that the plasma is optically thin, our results are valid for temperatures up to a few MeV. By contrast, classical transport theory begins to incur significant errors above k_{B}T∼10 keV, e.g., the parallel thermal conductivity is suppressed by 15% at k_{B}T=20 keV due to relativistic effects.


Beamed neutron emission driven by laser accelerated light ions

New Journal of Physics 18 (2016)

S Kar, A Green, H Ahmed, A Alejo, APL Robinson, M Cerchez, R Clarke, D Doria, S Dorkings, J Fernandez, SR Mirfayzi, P McKenna, K Naughton, D Neely, P Norreys, C Peth, H Powell, JA Ruiz, J Swain, O Willi, M Borghesi

© 2016 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.Highly anisotropic, beam-like neutron emission with peak flux of the order of 109 n/sr was obtained from light nuclei reactions in a pitcher-catcher scenario, by employing MeV ions driven by a subpetawatt laser. The spatial profile of the neutron beam, fully captured for the first time by employing a CR39 nuclear track detector, shows a FWHM divergence angle of ∼70°, with a peak flux nearly an order of magnitude higher than the isotropic component elsewhere. The observed beamed flux of neutrons is highly favourable for a wide range of applications, and indeed for further transport and moderation to thermal energies. A systematic study employing various combinations of pitcher-catcher materials indicates the dominant reactions being d(p, n+p)1 H and d(d,n)3He. Albeit insufficient cross-section data are available for modelling, the observed anisotropy in the neutrons' spatial and spectral profiles is most likely related to the directionality and high energy of the projectile ions.


A review of action estimation methods for galactic dynamics

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 457 (2016) 2107-2121

JL Sanders, J Binney


Rejuvenation of stellar mergers and the origin of magnetic fields in massive stars

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 457 (2016) 2355-2365

FRN Schneider, P Podsiadlowski, N Langer, N Castro, L Fossati


Thomson scattering measurement of a collimated plasma jet generated by a high-power laser system

Journal of Physics: Conference Series 688 (2016)

T Ishikawa, Y Sakawa, T Morita, Y Yamaura, Y Kuramitsu, T Moritaka, T Sano, R Shimoda, K Tomita, K Uchino, S Matsukiyo, A Mizuta, N Ohnishi, R Crowston, N Woolsey, H Doyle, G Gregori, M Koenig, C Michaut, A Pelka, D Yuan, Y Li, K Zhang, J Zhong, F Wang, H Takabe

© Published under licence by IOP Publishing Ltd.One of the important and interesting problems in astrophysics and plasma physics is collimation of plasma jets. The collimation mechanism, which causes a plasma flow to propagate a long distance, has not been understood in detail. We have been investigating a model experiment to simulate astrophysical plasma jets with an external magnetic field [Nishio et al., EPJ. Web of Conferences 59, 15005 (2013)]. The experiment was performed by using Gekko XII HIPER laser system at Institute of Laser Engineering, Osaka University. We shot CH plane targets (3 mm × 3 mm × 10 μm) and observed rear-side plasma flows. A collimated plasma flow or plasma jet was generated by separating focal spots of laser beams. In this report, we measured plasma jet structure without an external magnetic field with shadowgraphy, and simultaneously measured the local parameters of the plasma jet, i.e., electron density, electron and ion temperatures, charge state, and drift velocity, with collective Thomson scattering.


Poloidal tilting symmetry of high order tokamak flux surface shaping in gyrokinetics

PLASMA PHYSICS AND CONTROLLED FUSION 58 (2016) ARTN 045023

J Ball, FI Parra, M Barnes


The quiescent phase of galactic disc growth

Monthly Notices of the Royal Astronomical Society 459 (2016) 3326-3348

M Aumer, J Binney, R Schönrich

© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.We perform a series of controlled N-body simulations of growing disc galaxies within non-growing, live dark matter haloes of varying mass and concentration. Our initial conditions include either a low-mass disc or a compact bulge. New stellar particles are continuously added on near-circular orbits to the existing disc, so spiral structure is continuously excited. To study the effect of combined spiral and giant molecular cloud (GMC) heating on the discs, we introduce massive, short-lived particles that sample a GMC mass function. An isothermal gas component is introduced for a subset of the models. We perform a resolution study and vary parameters governing the GMC population, the histories of star formation and radial scale growth. Models with GMCs and standard values for the disc mass and halo density provide the right level of self-gravity to explain the age-velocity dispersion relation of the solar neighbourhood (Snhd). GMC heating generates remarkably exponential vertical profiles with scaleheights that are radially constant and agree with observations of galactic thin discs. GMCs are also capable of significantly delaying bar formation. The amount of spiral-induced radial migration agrees with what is required for the metallicity distribution of the Snhd. However, in our standard models, the outward-migrating populations are not hot enough vertically to create thick discs. Thick discs can form in models with high baryon fractions, but the corresponding bars are too long, the young stellar populations too hot and the discs flare considerably.


The nature and energetics of AGN-driven perturbations in the hot gas in the Perseus Cluster

Monthly Notices of the Royal Astronomical Society 458 (2016) 2902-2915

I Zhuravleva, E Churazov, P Arévalo, AA Schekochihin, WR Forman, SW Allen, A Simionescu, R Sunyaev, A Vikhlinin, N Werner

© 2016 The Authors.Cores of relaxed galaxy clusters are often disturbed by AGN. Their Chandra observations revealed a wealth of structures induced by shocks, subsonic gas motions, bubbles of relativistic plasma, etc. In this paper, we determine the nature and energy content of gas fluctuations in the Perseus core by probing statistical properties of emissivity fluctuations imprinted in the soft and hard-band X-ray images. About 80 per cent of the total variance of perturbations on ~8-70 kpc scales in the core have an isobaric nature, i.e. are consistent with subsonic displacements of the gas in pressure equilibrium with the ambient medium. The observed variance translates to the ratio of energy in perturbations to thermal energy of ~13 per cent. In the region dominated by weak 'ripples', about half of the total variance is associated with isobaric perturbations on scales of a few tens of kpc. If these isobaric perturbations are induced by buoyantly rising bubbles, then these results suggest that most of the AGN-injected energy should first go into bubbles rather than into shocks. Using simulations of a shock propagating through the Perseus atmosphere, we found that models reproducing the observed features of a central shock have more than 50 per cent of the AGN-injected energy associated with the bubble enthalpy and only about 20 per cent is carried away with the shock. Such energy partition is consistent with the AGN-feedback model, mediated by bubbles of relativistic plasma, and supports the importance of turbulence in the cooling-heating balance.


Numerical study of neutron beam divergence in a beam-fusion scenario employing laser driven ions

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 829 (2016) 176-180

A Alejo, A Green, H Ahmed, APL Robinson, M Cerchez, R Clarke, D Doria, S Dorkings, J Fernandez, P McKenna, SR Mirfayzi, K Naughton, D Neely, P Norreys, C Peth, H Powell, JA Ruiz, J Swain, O Willi, M Borghesi, S Kar

© 2016 Elsevier B.V.The most established route to create a laser-based neutron source is by employing laser accelerated, low atomic-number ions in fusion reactions. In addition to the high reaction cross-sections at moderate energies of the projectile ions, the anisotropy in neutron emission is another important feature of beam-fusion reactions. Using a simple numerical model based on neutron generation in a pitcher–catcher scenario, anisotropy in neutron emission was studied for the deuterium–deuterium fusion reaction. Simulation results are consistent with the narrow-divergence (∼70° full width at half maximum) neutron beam recently served in an experiment employing multi-MeV deuteron beams of narrow divergence (up to 30° FWHM, depending on the ion energy) accelerated by a sub-petawatt laser pulse from thin deuterated plastic foils via the Target Normal Sheath Acceleration mechanism. By varying the input ion beam parameters, simulations show that a further improvement in the neutron beam directionality (i.e. reduction in the beam divergence) can be obtained by increasing the projectile ion beam temperature and cut-off energy, as expected from interactions employing higher power lasers at upcoming facilities.


Erratum: Towards simulating star formation in turbulent high-z galaxies with mechanical supernova feedback [MNRAS, (2015), 451, 290]

Monthly Notices of the Royal Astronomical Society 459 (2016) 256-256

T Kimm, R Cen, J Devriendt, Y Dubois, A Slyz


SEARCH FOR PROMPT NEUTRINO EMISSION FROM GAMMA-RAY BURSTS WITH ICECUBE

ASTROPHYSICAL JOURNAL LETTERS 805 (2015) ARTN L5

MG Aartsen, M Ackermann, J Adams, JA Aguilar, M Ahlers, M Ahrens, D Altmann, T Anderson, C Arguelles, TC Arlen, J Auffenberg, X Bai, SW Barwick, V Baum, R Bay, JJ Beatty, JB Tjus, K-H Becker, S BenZvi, P Berghaus, D Berley, E Bernardini, A Bernhard, DZ Besson, G Binder, D Bindig, M Bissok, E Blaufuss, J Blumenthal, DJ Boersma, C Bohm, F Bos, D Bose, S Boeser, O Botner, L Brayeur, H-P Bretz, AM Brown, N Buzinsky, J Casey, M Casier, E Cheung, D Chirkin, A Christov, B Christy, K Clark, L Classen, F Clevermann, S Coenders, DF Cowen, AHC Silva, J Daughhetee, JC Davis, M Day, JPAM de Andre, C De Clercq, S De Ridder, P Desiati, KD de Vries, M de With, T DeYoung, JC Diaz-Valez, M Dunkman, R Eagan, B Eberhardt, T Ehrhardt, B Eichmann, J Eisch, S Euler, PA Evenson, O Fadiran, AR Fazely, A Fedynitch, J Feintzeig, J Felde, K Filimonov, C Finley, T Fischer-Wasels, S Flis, K Frantzen, T Fuchs, TK Gaisser, R Gaior, J Gallagher, L Gerhardt, D Gier, L Gladstone, T Gluesenkamp, A Goldschmidt, G Golup, JG Gonzalez, JA Goodman, D Gora, D Grant, P Gretskov, JC Groh, A Gross, C Ha, C Haack, AH Ismail, P Hallen, A Hallgren, F Halzen, K Hanson, D Hebecker, D Heereman, D Heinen, K Helbing, R Hellauer, D Hellwig, S Hickford, GC Hill, KD Hoffman, R Hoffmann, A Homeier, K Hoshina, F Huang, W Huelsnitz, PO Hulth, K Hultqvist, A Ishihara, E Jacobi, J Jacobsen, GS Japaridze, K Jero, O Jlelati, M Jurkovic, B Kaminsky, A Kappes, T Karg, A Karle, M Kauer, A Keivani, JL Kelley, A Kheirandish, J Kiryluk, J Klaes, SR Klein, J-H Koehne, G Kohnen, H Kolanoski, A Koob, L Koepke, C Kopper, S Kopper, DJ Koskinen, M Kowalski, A Kriesten, K Krings, G Kroll, M Kroll, J Kunnen, N Kurahashi, T Kuwabara, M Labare, JL Lanfranchi, DT Larsen, MJ Larson, M Lesiak-Bzdak, M Leuermann, J Luenemann, J Madsen, G Maggi, R Maruyama, K Mase, HS Matis, R Maunu, F McNally, K Meagher, M Medici, A Meli, T Meures, S Miarecki, E Middell, E Middlemas, N Milke, J Miller, L Mohrmann, T Montaruli, R Morse, R Nahnhauer, U Naumann, H Niederhausen, SC Nowicki, DR Nygren, A Obertacke, S Odrowski, A Olivas, A Omairat, A O'Murchadha, T Palczewski, L Paul, O Penke, JA Pepper, CP de los Heros, C Pfendner, D Pieloth, E Pinat, J Posselt, PB Price, GT Przybylski, J Puetz, M Quinnan, L Raedel, M Rameez, K Rawlins, P Redl, I Rees, R Reimann, M Relich, E Resconi, W Rhode, M Richman, B Riedel, S Robertson, JP Rodrigues, M Rongen, C Rott, T Ruhe, B Ruzybayev, D Ryckbosch, SM Saba, H-G Sander, J Sandroos, M Santander, S Sarkar, K Schatto, F Scheriau, T Schmidt, M Schmitz, S Schoenen, S Schoeneberg, A Schoenwald, A Schukraft, L Schulte, O Schulz, D Seckel, Y Sestayo, S Seunarine, R Shanidze, MWE Smith, D Soldin, GM Spiczak, C Spiering, M Stamatikos, T Stanev, NA Stanisha, A Stasik, T Stezelberger, RG Stokstad, A Stoessl, EA Strahler, R Stroem, NL Strotjohann, GW Sullivan, H Taavola, I Taboada, A Tamburro, A Tepe, S Ter-Antonyan, A Terliuk, G Tesic, S Tilav, PA Toale, MN Tobin, D Tosi, M Tselengidou, E Unger, M Usner, S Vallecorsa, N van Eijndhoven, J Vandenbroucke, J van Santen, M Vehring, M Voge, M Vraeghe, C Walck, M Wallraff, C Weaver, M Wellons, C Wendt, S Westerhoff, BJ Whelan, N Whitehorn, C Wichary, K Wiebe, CH Wiebusch, DR Williams, H Wissing, M Wolf, TR Wood, K Woschnagg, DL Xu, XW Xu, Y Xu, JP Yanez, G Yodh, S Yoshida, P Zarzhitsky, J Ziemann, M Zoll


A fast algorithm for estimating actions in triaxial potentials

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 447 (2015) 2479-2496

JL Sanders, J Binney


Simulation of density measurements in plasma wakefields using photon acceleration

PHYSICAL REVIEW SPECIAL TOPICS-ACCELERATORS AND BEAMS 18 (2015) ARTN 032801

MF Kasim, N Ratan, L Ceurvorst, J Sadler, PN Burrows, R Trines, J Holloway, M Wing, R Bingham, P Norreys


Investigation of the solid-liquid phase transition of carbon at 150 GPa with spectrally resolved X-ray scattering

HIGH ENERGY DENSITY PHYSICS 14 (2015) 38-43

J Helfrich, D Kraus, A Ortner, S Frydrych, G Schaumann, NJ Hartley, G Gregori, B Kettle, D Riley, DC Carroll, MM Notley, C Spindloe, M Roth


INEFFICIENT DRIVING OF BULK TURBULENCE BY ACTIVE GALACTIC NUCLEI IN A HYDRODYNAMIC MODEL OF THE INTRACLUSTER MEDIUM

ASTROPHYSICAL JOURNAL 815 (2015) ARTN 41

CS Reynolds, SA Balbus, AA Schekochihin


Action-based distribution functions for spheroidal galaxy components

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 447 (2015) 3060-3068

L Posti, J Binney, C Nipoti, L Ciotti


Intrinsic alignment of simulated galaxies in the cosmic web: implications for weak lensing surveys

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 448 (2015) 3391-3404

S Codis, R Gavazzi, Y Dubois, C Pichon, K Benabed, V Desjacques, D Pogosyan, J Devriendt, A Slyz